RESEARCHES INTO ANTHROPOLOGICAL HEREDITY 197 



and 1 plain brown eyes. To conclude from this case that the light 

 mixed eyes type is dominant to the blue type is difficult. 



The relation of the dark mixed eyes to the blue type is quite 

 different. I have 9 couples of that kind with 21 children. 10 of these 

 children have pigmented eyes while 11 have blue ones. These dark 

 mixed eyes seem therefore to be heterozygotes dominating the blue 

 type when interbred (DR X RR = 2 DR X 2 RR). — I have not touched 

 on the mode of inheritance of the plain brown type from the very 

 good reason that my material give no information on this point. As 

 a matter of fact, the plain brown type is very rarely found, particu- 

 larly so in Selbu. And those eyes in which the plain brown type is 

 found seem to have the type very much weakened. They are extre- 

 mely light compared to those found in races with genuine brown eyes. 



I have only met with one family where both parents had brown 

 eyes. In this family half of the children had plain brown eyes, the 

 other half plain blue eyes. The brown parents must therefore both 

 have been heterozygotes. The mode of inheritance of the brown eye 

 colour has been so thoroughly studied elsewhere that it must be con- 

 sidered fairlv well known. 



The result of the research may be summed up under the following 

 heads: 



1. If both parents and all the grand-parents have blue eyes (without 

 brownish pigment), all the children will have blue eyes. 



2. If both parents have blue eyes while some of the grandparents 

 have eyes with brownish pigment, some of the children (ca 10 % ) 

 will also have ej^es with brownish pigment, while the rest will 

 have blue ones. 



3. If both parents have eyes with brownish pigment, an average of 

 V4 of the children will have blue eyes and V4 will have eyes with 

 brownish pigment. 



4. If one of the parents has brownish-coloured eyes, the other having 

 blue ones, there will be an average of V2 of the children with blue 

 eyes and ^/o with brown eyes. -^'t 



5. If both parents have »mixed » eyes, an average of Vi of the children 

 will have blue eyes, V4 plain brown eyes and '/i »mixed» eyes. 

 This rule is perhaps not applicable to all types of »mixed» eyes. 

 So it does hot seem to apply to blue eyes with a well defined 

 brown ring around the pupil. If both parents have this special 



